In a cellular radio system (such as, by way of non-limiting example, 3GPP. LTE, 3G and 4G), wireless terminals (also known as mobile stations and/or user equipment units (UEs)) communicate via a radio access network (RAN) to one or more core networks (such as, by way of non-limiting example, the Evolved Packet Core (EPC) network).
UEs may be (by way of non-limiting example) mobile telephones (“cellular” telephones), desktop computers, laptop computers, tablet computers, and/or any other devices with wireless communication capability to communicate voice and/or data with a RAN. To access the cellular network, the UE has a Subscriber Identity Module (SIM) or Universal Integrated Circuit Card (UICC) that has an associated International Mobile Subscriber Identity (IMSI) and other subscriber information, which is assigned by the operator network to a subscriber. A UE with SIM/UICC credentials (hereinafter referred to as a subscribing wireless device/UE) can authenticate and operate in a RAN and gain access to core network services. In some examples, the SIM/UICC allows the UE to perform Extensible Authentication Protocol (EAP) authentication (including, without limitation, EAP-SIM, EAP-AKA, or EAP-AKA′ protocols) against an operator's 3GPP AAA/HSS/HLR. When the UE is used for data communications via the RAN, the UE is assigned one or more Internet Protocol (IP) addresses. Some UEs are also capable of communicating data via a wireless local area network (WLAN). Such UEs are sometimes referred to as dual-mode UEs. This dual mode capability permits the UE to engage in data communications along a WLAN when and where available, to reduce the amount of data communications across the RAN, to gain better data throughput over the WLAN, and/or to reduce the fees charged over the RAN.
In some example embodiments, the data communications bandwidth available to the dual mode UE may be greater along a WLAN than along the RAN. In some example embodiments, the unit cost of data communications may be smaller along a WLAN than along the RAN. Thus, in some example embodiments, the dual mode UE may be permanently or in specific situations, or upon user preference or specification, configured to prefer data communications along a connected WLAN rather than along the RAN.
In some embodiments, network operators have deployed WLANs that substantially overlap a RAN or portion thereof. The WLAN together with the EPC, provide services including authentication, policy, charging and IP mobility for subscribing dual mode UEs and WLAN devices.
The architecture for so-called Trusted WLAN Access Networks (TWANs) is described in section 16.1.1 of 3GPP TS 23.402, V12.3.0, 2013-12: “Architecture enhancements for non-3GPP accesses” (TS 23.402), which is incorporated by reference in its entirety herein. The TWAN is interfaced with the EPC via the STa interface to the 3GPP AAA Server/Proxy and with the PDN Gateway (PGW) via the S2a interface.
FIG. 1 shows an example of a subscribing UE 10 configured to operate with an EPC 18 via a RAN node 20 (e.g. in the case of LTE, an eNodeB) in a RAN The EPC 18 includes a PGW 14 and an Authentication, Authorization and Accounting (AAA) server (or proxy) 16 which itself can connect with network resources of a home operator (e.g. Home Location Register (HLR)/Home Subscriber Server (HSS)) to perform AAA procedures for the UE 10. In that example, the subscribing UE 10 is a dual-mode device that is also configured to operate with the EPC 18 via a TWAN access node 12. The UE 10 also has a separate radio (not shown), by which it can operate as a Wi-Fi access point (e.g. a hotspot), enabling other WLAN (e.g. TWAN) devices (22, 24, 26) to connect to the UE 10 and employ the UE's data communications capabilities.
The UE 10 can also use its separate radio to connect to the EPC 18 via a TWAN node 12 in a TWAN (13). Connecting a WLAN device (22, 24, 26), including dual mode UE 10, to a WLAN, including a TWAN, involves selecting a Service Set Identifier (SSID) of the network and connecting thereto. In some example embodiments, the SSID of a WLAN is made visible so that it becomes available to any WLAN device in the network's coverage area, so that the WLAN device may automatically, or upon user input, select the SSID.
In some example embodiments, the WLAN does not make its SSID visible and is said to be hidden. Rather, the WLAN device knows and specifies the WLAN's SSID in order to connect to it.
WLANs may, in some example embodiments, be hidden. In some example embodiments, WLANs may establish an AAA procedure with a connecting dual mode UE (e.g. UE10), using EAP authentication against the operator's AAA/HSS/HLR, over the WLAN, as described in section 6.1 of 3GPP TS 33.234, V11.4.0, 2012-06: “Wireless Local Area Network (WLAN) interworking security” (TS 33.234), which is incorporated by reference herein in its entirety.
With successful authentication, the UE 10 is authorized to use its assigned IMSI to gain access to the operator's EPC 18 via the TWAN node 12 to obtain various EPC services or to receive other services offered by the operator at the TWAN such as a Non-seamless WLAN Offload (NSWO) service, as instructed by the AAA.
Turning now to FIG. 2, there is shown a signaling diagram demonstrating establishment of a GTP 32a session for a connecting device (in this case the subscribing UE 10) between the TWAN access node 12 and the PGW 14 of FIG. 1. Further details may be found in section 16.2.1 of TS 23.402, which is incorporated in its entirety herein. At step 1000, the UE 10 establishes an association with the TWAN access node 12. That procedure is governed by Section 4.10.3 of IEEE 802.11-2012 “IEEE Standard for Information Technology—Telecommunication and Information Exchange between Systems 802.11-2012-IEEE Standard for Information technology—Telecommunications and information exchange between systems Local and metropolitan area networks—Specific requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications. Once the UE is associated with the TWAN node 12, it then attempts to authenticate against the AAA server 16 at step 1002 using the UE's SIM/USIM credentials. The AAA server 16 then operates to retrieve user subscription and authentication information from a HSS/HLR server of a home operator (step 1003). After successful EAP authentication of the UE 10, the AAA server 16 sends the authorized IMSI (ie. the UE's IMSI) and other information (e.g. an APN) to the TWAN access node 12.
With that information, the TWAN access node 12 sends a Create Session Request message at step 1004 to the PGW 14 to establish an S2a session. The message contains the authorized UE's IMSI and an APN provided by the AAA server 16, as well as other parameters necessary to establish the S2a session such as, for example, an Evolved Packet System (EPS) Bearer Identity (e.g. EPS-ID-X) and a default EPS Bearer Quality of Service (QoS). The EPS Bearer Identity and default EPS Bearer QoS parameters convey the default S2a bearer QoS. In response, at step 1006, the PGW 14 returns a Create Session Response message to the TWAN node 12 containing an IP address for the UE 10. At step 1008, the Dynamic Host Control Protocol (DHCP) allows the UE 10 to obtain the newly assigned IP address via the TWAN node 12.
As mentioned above, some UEs, which may or may not be dual mode UEs, have a separate radio, by which it can operate as a Wi-Fi access point (e.g. a hotspot), enabling other WLAN devices (e.g. WLAN devices 22, 24, 26 of FIG. 1) to connect to the UE and employ the UE's data communications capabilities, including its cellular network connection, to access the internet and other subscribed services. Such other devices are said to be tethered to the cellular network and are known as Tethered Equipment (TE), and may comprise computers, including desktop, laptop, netbook and/or tablet computers, cellular phones, portable devices such as e-book readers, digital music and/or video players, cameras, game controllers and/or devices and other UEs.
This Wi-Fi hotspot capability may be useful when the TE does not have access to an existing visible or hidden WLAN, including a TWAN. However, to provide this hotspot capability, the UE performs data communications through both its cellular radio and its hot-spot radio, which may rapidly decrease the battery life of the UE. Additionally, the TE occupies additional cellular bandwidth of the UE, the cost of which would be borne by the UE subscriber.
These issues are compounded by the proliferation of WLAN devices. Increasingly, users have multiple devices and scenarios may be envisaged where a single (subscribing) UE tethers multiple TEs.
Where the subscribing UE is a dual mode UE and there is an available WLAN, which may be a TWAN, the possibility exists that a WLAN device, such as a TE, could access the WLAN directly. If the WLAN device does not have or is not provisioned with its own SIM or UICC containing SIM/Universal Subscriber Identity Module (USIM) credentials (ie. Hereinafter referred to as a non-subscribing wireless/WLAN device), the WLAN device may not be able to authenticate and gain access to subscribed EPC/WLAN services. To address this situation, Section 6.7 of TS 33.234, which is incorporated by reference in its entirety herein, provides a method for a (non-subscribing) WLAN device to use a subscribing UE's SIM USIM credentials, and perform EPA-SIM, AKA or AKA′ authentication against the operators EPC in the context of a TWAN.
Once the authentication process has been successfully completed, a non-subscribing WLAN device can thereafter connect to the WLAN and obtain services (e.g. from the EPC), as if it were the subscribing UE. Indeed, from the perspective of the WLAN, the WLAN device is indistinguishable from the subscribing UE.
The fact that conventionally, from the perspective of the WLAN, the non-subscribing WLAN device is indistinguishable from the subscribing UE limits the capabilities that are offered by the operator to the subscribing UE and the non-subscribing WLAN device. By way of non-limiting example, four limits on capabilities are identified:                1. Traffic steering: In some example embodiments, for a dual mode UE, the operator's cellular network may in fact provide improved data bandwidth rather than the corresponding WLAN. In such circumstances, the operator network may provide a capability, whether permanently or in specific situations, or upon user preference or specification, whereby the subscribing UE is not admitted to the WLAN. Additionally, or alternatively, while the subscribing UE is connected to the WLAN, where the subscribing UE's throughput is detected as having become worse than it would have been through the cellular network, the operator network may provide a capability, whether permanently or in specific situations, or upon user preference or specification, whereby the WLAN disassociates the admitted subscribing UE. This capability is known as traffic steering and provides that the subscribing UE is attached to the better performing data network.        When a WLAN device is connected to the WLAN, if such traffic steering capability is enabled, the operator network may mistakenly assume that the non-subscribing WLAN device is the subscribing UE, because the devices share the subscribing UE's IMSI and are, to the WLAN, indistinguishable. As such, if the throughput experienced by the WLAN device is less than what the subscribing UE would have experienced through the cellular network, the operator network may attempt to disassociate the non-subscribing WLAN device. However, in some example embodiments, the non-subscribing WLAN device lacks an ability to access a cellular network, so that the non-subscribing WLAN device's data connection would be severed. In this case, it would be beneficial to identify the devices as being a non-subscribing WLAN device or a subscribing UE.        2. S2a session: In order for each device to access EPC services, it would be advantageous to differentiate the various devices. Otherwise, only the first device (whether the subscribing UE or one of the non-subscribing WLAN devices) to connect to the WLAN may access the EPC services.        3. IP mobility continuity: Because the subscribing UE and non-subscribing WLAN device are mobile devices, and may move between cells, access points, WLANs, cellular networks and/or between a WLAN and a cellular network (either manually, or automatically, such as for example, as discussed above in the context of traffic steering), it would be advantageous to maintain the IP address assigned to the device(s), in order to avoid interruption of the data communications, for example, during the course of a download of video or other content.        4. Core network connection: In some example embodiments, it would be advantageous for the network operator to enable individual policies for each device and/or to separately monitor and/or charge for EPC services. Absent a mechanism for differentiating the subscribing UE from other devices that might use the UE's credentials to authenticate, the devices would share a common policy and the UE subscriber may not be able to obtain differentiated services for its devices and/or may not be able to obtain separate billing information.        